Lab Analysis Flashcards
What does distillation do?
- Separates 2 or more liquids based on boiling points
What does simple distillation do?
- Separate liquids with boiling point difference equal to or over 50C
What does fractional distillation do?
- Separate liquids with boiling point difference less than 50C
How is calibration factor found?
- Found by performing a chemical reaction in calorimeter that releases known quantity of thermal energy + measuring the resultant temperature rise
Infrared spectroscopy: Molecule interaction with energy source
- Absorbs infrared radiation
Infrared spectroscopy: Effect on Molecule
- Increase in bond vibration
Infrared spectroscopy: Information obtained from technique
- Functional groups
HNMR and CNMR spectroscopy: Molecule interaction with energy source
- Absorption of radio waves
HNMR and CNMR spectroscopy: Effect on Molecule
- Increase in nuclear spin energy level
HNMR and CNMR spectroscopy: Information obtained from technique
- No. of Carbon-Hydrogen environments
- No. of Hydrogens on neighbouring Carbon
Mass spectroscopy: Molecule interaction with energy source
- Collision with high energy electrons
Infrared spectroscopy: Effect on Molecule
- Fragmentation of molecules
Mass spectroscopy: Information obtained from technique
- Molar mass
What is a fragment ion?
- A positively charged molecule fragment
What is a fragment radical?
- The other molecule formed alongside the fragment ion
What is an isotope?
- An atom of the same element with a different molecular mass
What is meant by m/z value?
Mass to Charge Ratio
How do you test for Carbon=Carbon bonding?
- Undergoes addition reaction with halogens/di-halogens, etc…
- The mixture will change colour rapidly
How do you test for the presence of hydroxyl groups?
- Add heat and ACIDIFIED Dichromate/Permanganate:
~ A colour change will occur in the presence of a hydroxyl group (unless tertiary)
- Turns red litmus paper blue
How do you test for the presence of carboxyl groups?
- Addition of sodium hydrogen carbonate (NaHCO3)
- Lime water tests for CO2
- Turns blue litmus paper red
What is the mobile phase of HPLC and what are its properties?
- The moving phase
- Is polar
- Molecules desorb into mobile phase
What is the stationary phase of HPLC and what are its properties?
- The non-moving phase
- Is non-polar
- molecules adsorb into stationary phase
What is the use of the stationary phase of HPLC
- Used to slow down the movements of particles based on polarity and size to see how they separate.
In HPLC, polar molecules…
…move faster because they are in the mobile phase more often
- Lower retention time for smaller, more polar molecules
- Polar mobile phase attracts molar molecules
Which peak tells us the molar mass of the parent molecule?
The molecular ion peak(s)
- Yes, there can be multiple
Explain how the molecular ion peaks in the mass spectrum relate to the molecular mass of a molecule
- The relative molar mass of a molecule is the weighted average of these molecular ion peak abundances.
Explain why different frequencies of infrared radiation can be absorbed by the same molecule
- Due to functional groups
- Different functional groups have different bond strengths, bond lengths, and different bond vibrations when exposed to infrared radiation
Relative peak area…
… indicates the number of hydrogens in a particular environment
